This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-009325, filed Jan. 17, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an electric circuit having a liquid crystal display element and an image pick-up element and more particularly, to an active matrix type electric circuit driven by a shift register.
2. Description of the Related Art
In a TFT liquid crystal display device, a TFT (Thin Film Transistor) that is an active element is provided for each pixel, and data is written into a pixel capacitance by turning ON/OFF the TFT, thereby displaying a desired image. In order to thus display such an image, in general, the TFT liquid crystal display device has a driver circuit having a gate driver and a drain driver.
The gate driver sequentially selects one of a plurality of gate lines in the TFT liquid crystal display device, and widely uses a shift register composed of a plurality of transistors. In some of such shift registers, an operation of each stage that corresponds to each gate line is controlled by a signal generated at its preceding or following stage.
An output signal outputted to a gate line of a liquid crystal element from each stage of such a shift register is damped by a distributed parameter circuit defined by the gate line and the TFT, pixel capacitance, and compensation capacitance connected to the gate line. Therefore, the distributed parameter circuit caused by each gate line and elements connected to such each gate line affects a circuit operation of the shift register.
If the number of stages of the shift resister is the same as that of lines in display pixels of the TFT liquid crystal display element, a circuit operation at the last stage is not affected by a circuit operation at the next stage, unlike the other stage. Therefore, in the circuit operation at the last stage, there occurs a slight difference from circuit operation at the preceding stage. Further, if the circuit is driven for a long period of time, there has been a problem that such a slight difference is considered as gradually affecting the preceding stages, and operation of the shift register configuring a gate driver becomes unstable.
It is an object of the present invention to provide an electric circuit such that a shift register applied as a driver is stably operated.
It is another object of the present invention to provide an electric circuit such that an area of elements formed outside of a display region or outside of an image pick-up element region is reduced, and such that the elements make the electric circuit stable.
According to one aspect of the present invention, there is provided an electric circuit comprising:
a plurality of wires provided in a display region on a substrate;
a plurality of display pixels provided at the plurality of wires, respectively;
a dummy wire (single) provided in a non-display region on the substrate;
According to another aspect of the present invention, there is provided an electric circuit comprising:
a plurality of wires provided on a substrate;
a plurality of image pick-up elements provided at a respective one of the plurality of wires;
a dummy wire (single) provided in a dummy element region on the substrate; and
a dummy element (single) connected to the dummy wire so that a parasitic capacitance at a respective one of the plurality of wires is equal to that at the dummy wire.
In the above described electric circuit, a wiring load capacity in a region in which the plurality of display pixels or a plurality of image pick-up elements are formed is equal to a dummy wiring load capacity in a non-display region or dummy element region. Thus, even if stages of drivers used for a plurality of wires and dummy wire each are affected by the preceding and following stages, a stage corresponding to a respective one of a plurality of wires in a pixel region or image pick-up element region can be constantly operated without being affected by the preceding and following stages. Thus, a plurality of wires and dummy wires can be constantly selected.
In such an electric circuit, there may be provided a load having circuit characteristics equivalent to those of a circuit formed by an active element, a pixel capacitance, and a compensation capacitance that has been directly or indirectly connected. In addition, each stage of a shift register scanning the electric circuit may be constructed by using a combination of an electric field effect transistor formed in the same process as that in the active element.
The above described electric circuit may not be provided and the load may be set so as to provide circuit characteristics equivalent to those of a circuit formed by each scanning line and the parasitic capacitance and pixel capacitance of an active element that has been directly or indirectly connected.
In this way, when the capacity of a dummy capacitance equals a composite capacity of a pixel capacitance (or image pick-up element capacitance) and a compensation capacitance is formed, an area of a load occupied on a substrate can be reduced more significantly than that when a structure identical to that of each of these capacities is formed a load. Namely, a capacity consisting of the pixel capacitance (or image pick-up element capacity and compensation capacitance and a circuit having characteristics equivalent to those of a circuit composed of a wiring resistor can be formed to be very small by a width substantially corresponding to that of dummy wire. In this manner, a region in which pixels are formed, i.e., a rate of display area can be increased. Adjustment between a resister value and a capacity value can be made by adjusting a width of a dummy wire and a length of a dummy capacitance electrode.
According to another aspect of the present invention, there is provided an electric circuit comprising:
pairs (plural) of first wires and second wires provided in an image pick-up element region on a substrate;
image pick-up elements (plural) provided at a respective one of pairs (plural) of the first wires and second wires;
a pair (single) of a first dummy wire and a second dummy wire provided in a dummy element region on the substrate;
a dummy element (single) connected to a pair (single) of the first dummy wire and second dummy wire so that a parasitic capacitance of a respective one of pairs (plural) of the first wire and second wire is equal to that in a par (single) of the first dummy wire and second dummy wire; and
a shift register connected to pairs (plural) of the first wires and second wires provided in the image pick-up region and a pair (single) of the first dummy wire and second dummy wire provided in the dummy element region, where the shift register has a plurality of stages according to pairs (plural) of the first wires and second wires and a pair (single) of the first dummy wire and second dummy wire, and at least part of the plurality of stages is driven according to an output signal from a next stage of the stage.
In the above described electronic device, there is provided a dummy element such that a capacity in pairs of first wires and second wires for driving image pick-up elements is equal to that in a pair (single) of first dummy wire and second dummy wire. Thus, even in the case where at least part of a plurality of stages of the shift register is driven in response to an output signal from at least part of a plurality of stages according to a pair (single) of first dummy wire and second dummy wire, signal characteristics in pairs of the first wires and second wires and signal characteristics in pair of first dummy wire and second dummy wire are uniform. Thus, the electronic device can be normally driven at a plurality of stages.
In addition, even if a signal supplied to an auxiliary dummy stage is set to be identical to that supplied to a plurality of wires, constant driving can be carried out. Thus, there is no need to set a new voltage value or amplitude signal for a dummy stage. Therefore, a voltage generator circuit and a wiring design can be simplified.